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ANTHRAQUINONE                            225

tion is cooled to 20 and stirred mechanically whilst the nitric
acid is run in drop by drop. As the temperature should not
rise above 40 it will be found necessary at the beginning to
cool the vessel in a freezing mixture. After the nitric acid&has
been added the stirring is continued for another I hour and the
product is then left overnight. The naphthol yellow crystallises
out and is filtered and washed with small quantities of a cold,
saturated solution of salt. The precipitate is then dissolved in a
large basin of hot water and potassium carbonate solution added
until the liquid gives an alkaline reaction. On cooling, the
potassium salt separates in small orange needles, and is filtered
and dried on a porous plate. Yield, 2025 grams.
C10H7OH 4- 3H2S04 = C10H4(OH)(S03H)3.
C10H4(OH)(SO,,H)3 + 2HN03 = C10H4(OH)(NO.,)2SO3H
+2H2SO4.
2C10H4(OH)(N02)2S03H + KSC03 = 2C10H4(OH)(NO9),S03K
+ C02 + H20.
See Appendix) p. 315.
PREPARATION 108.
Anthraquinone, C(JH4<
Graebc, Liebermann, Annalen, SpL, 1869, 7, 284.
10 grms. anthracene (pure).
120 c.c. glacial acetic acid.
20 grins, chromium trioxide dissolved in 15 c.c. water, and
then 75 c.c. glacial acetic acid added.
The anthracene is dissolved in the acetic acid by boiling them
together in a round flask (| litre) with upright condenser over
wire-gauze. The solution of chromium trioxide is then dropped
in from a tap-funnel pushed into the top end of the condenser
whilst the liquid is kept boiling. The operation should last about
an hour. The solution becomes a deep green. It is allowed to
cool and poured into water (500 c.c.), which precipitates the
anthraquinone in the form of a brown powder. After standing an
hour, it is filtered through a large fluted filter, washed with a little
COHEN'S ADV. P. o. c.                                             Q